Control systems for vehicle engines and transmissions, in particular of motor vehicles having an automated transmission, are being continually further developed and improved upon. In the process, the following functions are attributed for the most part to the modern transmission control:
shift control for a smooth and wear-free gear shifting;
control of the (torque) converter lockup clutch;
shift logic, which determines the gear to be engaged;
self-diagnostics; and
basic functions, such as input and output functions.
German Patent Application No. DE 44 41 896 describes a control system having a transmission control designated therein as xe2x80x9csmart ratio change unitxe2x80x9d, which is mounted on the transmission of the vehicle in order to directly control the hydraulic valves (actuators) there. Moreover, an engine management is provided, which is connected to the transmission control via a communications channel configured as a CAN data bus to exchange data with the transmission control. The extent to which signal lines are used, i.e., the outlay for the vehicle""s wiring harness, is reduced by mounting the transmission control directly on the transmission housing and by using a data bus. Arranged moreover in the passenger compartment is a plurality of electrical shifting components, such as a selector lever switch, a kickdown switch, or a driving program selector (shift mode button), which transmit different switch point and sensor signals to the transmission control via numerous single lines.
An object of the present invention is to improve the aforementioned control system in a way that will again significantly reduce the use of single signal lines using a simplest possible contacting and connecting technique. A vehicle equipped with such a control system is also described.
Therefore, the electrical shifting components located in the passenger compartment are connected via signal lines to an electronic control unit, which is located in the passenger compartment and connected to the data bus, and which combines the signals transmitted over the signal lines, routing them via the data bus to the transmission control.
This means that the numerous signal lines do not need to be laid directly to the transmission control, but merely to the electronic control unit, which is likewise located in the passenger compartment and assumes the function of a series-connected, processor-controlled line concentrator that is linked to the transmission control via the data bus. The outlay for the wiring harness is again clearly diminished, with the data bus now also being routed into the passenger compartment, enabling additional devices to be connected thereto. Accordingly, the control system can be easily expanded.
It is particularly advantageous for the electronic control unit to be a microprocessor-controlled instrument cluster, located on the dashboard or in the passenger compartment of the vehicle. This enables an already existing instrument cluster to be used for the concentrator function in that it is merely expanded by a processor-controlled bus port having plug-in connections, as well as input and output functions. The result is an especially cost-effective realization of the present invention.
In addition, in the event that the transmission is an automatic multiple-ratio transmission or a continuously variable transmission, it is particularly advantageous for electrohydraulic modules that shift the transmission to be integrated in the transmission control. This achieves a high level of integration of electrical and hydraulic components and keeps the amount of cabling at the transmission housing to a minimum. In this context, a special, additional advantage is derived when the transmission control and the engine management are combined into one central control system located in the engine compartment of the vehicle.
Another special advantage is derived when a (communication) security line is installed in the vehicle in parallel to the data bus for additionally transmitting the signals to be transmitted using a modulation process, particularly a pulse-width modulation process. This enables the control system to remain fully intact in the event of a transmission disturbance on the data bus. In this context, the modulation process, which is preferably a pulse-width modulation process, renders possible a fail-safe transmission of a multiplicity of signals over this one security line.